A light curing material that is cured by irradiation with light is known. The light curing material has advantages such that this is cured in a short time, curable without increasing temperature of an irradiated object, and environmentally friendly. Therefore, the light curing materials are used in various applications such as bonding of electronic parts or optical parts, printing technology using the light curing materials as printing ink, and the like.
In addition, an exposure technology of performing microfabrication using light is known. The exposure technology is used, for example, for manufacturing an electrode pattern of an LED and in a manufacturing process of micro electro mechanical systems (MEMS) represented by an acceleration sensor.
In these technologies, a discharge lamp with high luminance has been used as a light source. However, with the progress of a solid-state light source technology in recent years, it is studied to use a light source obtained by arranging a plurality of light emitting elements such as LED elements in place of a discharge lamp.
FIG. 9 illustrates a light irradiation device 100 in Patent Document 1. The light irradiation device 100 includes light emitting units (103, 104, 105, 106, 107, and 108) arranged in two rows and three columns. Each of the light emitting units is formed of eight light emitting elements 109 connected in series. Each light emitting unit is connected in parallel to a power supply. In addition, the light emitting elements 109 are arranged in an x direction and a y direction at an interval of 4.6 mm. In each of the light emitting units (103, 104, and 105) in a first row, the light emitting element 109 located on a left end of the drawing is connected to an anode side of the power supply, and the light emitting element 109 located on a right end of the drawing is connected to a cathode side of the power supply. In each of the light emitting units (106, 107, and 108) in a second row, the light emitting element 109 located on the right end of the drawing is connected to the anode side of the power supply, and the light emitting element 109 located on the left end of the drawing is connected to the cathode side of the power supply.